[Qemu-discuss] The Details about TranslationBlock

[田泽轶]

Hi All,

   I've been reading the source code of qemu for few days.

   I wanna figure out the real meaning about some variables of TranslationBlock.

   such as:

   uint16_t tb_next_offset[2]; /* offset of original jump target */

   #ifdef USE_DIRECT_JUMP

   uint16_t tb_jmp_offset[4]; /* offset of jump instruction */

   #else

   uintptr_t tb_next[2]; /* address of jump generated code */

   #endif

   struct TranslationBlock *jmp_next[2];

   struct TranslationBlock *jmp_first;

   uint32_t icount;

   

   tb_jmp_offset[4], I don't really know what the number "4" means about.

   *jmp_next[2], the document told me that the "2" is a boundary about "taken" or "not taken", but How will the TB have a "not taken" branch?

    

   I'm trying to understand the meaning of these variables.

   Appreciate any help in this regard.

   Thanks,

   -Stany